PFG NMR Self-Diffusion Measurements with Large Field Gradients

Heink, W.; Kärger, Jörg; Seiffert, G.; Fleischer, G.; Rauchfuss, J.

doi:10.1006/jmra.1995.1112

Cited by 36 publications

(21 citation statements)

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“…a cell, the experimental results depend on the local self-diffusion coefficient D 0 and the pore size and shape [8][9][10][11]. When trying to measure D 0 using PGSE NMR, the traditional approach has been to decrease the experimentally defined observational time scale, the diffusion time, in order to reduce the influence of collisions with the pore walls [12,13]. The analysis of PGSE NMR data is often based on the short gradient pulse (SGP) approximation which states that the molecular displacements taking place during the diffusion-encoding gradient pulses are insignificant in comparison to both the pore size and the displacements during the diffusion time [4,14,15].…”

Section: Introductionmentioning

confidence: 99%

Determination of the self-diffusion coefficient of intracellular water using PGSE NMR with variable gradient pulse length

Åslund

Topgaard

2009

Journal of Magnetic Resonance

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Section: Introductionmentioning

confidence: 99%

Determination of the self-diffusion coefficient of intracellular water using PGSE NMR with variable gradient pulse length

Åslund

Topgaard

2009

Journal of Magnetic Resonance

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“…The PFG NMR experiments were carried out with a home-built NMR spectrometer [27,28] operating at a 1 H-resonance frequency of 400 MHz. In each experimental run, τ was chosen to be 3 ms, δ and t were fixed and g was incremented.…”

Section: Methodsmentioning

confidence: 99%

Self-diffusion of poly(propylene glycol) in nanoporous glasses studied by pulsed field gradient NMR: A study of molecular dynamics and surface interactions

Schönhals

Rittig

Kärger

2010

The Journal of Chemical Physics

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Pulsed field gradient NMR is applied to investigate the self-diffusion of poly(proypylene glycol) in nanoporous glasses (nominal pore sizes of 2.5-7.5 nm). In general, the diffusion is slowed down by the confinement compared to the bulk. For native pore surfaces covered by hydroxyl groups the spin echo attenuation Ψ displays a bimodal behavior versus q(2)t (q-norm of a generalized scattering vector). This was explained assuming spatial regions of different diffusivities in a two-phase model. The slow component is assigned to segments forming a surface layer close to the pore walls in which the segments have a lower mobility than those located in the center of the pores. By variation of observation time it was concluded that time constant for the dynamic exchange of segments between these two regions is around 100 ms at room temperature. For silanized pores, the bimodal behavior in the spin echo attenuation Ψ shows a stretched exponential decay versus q(2)t. The estimated diffusion coefficients decrease strongly with decreasing pore size. The temperature dependence of the diffusion coefficient can be approximated by an Arrhenius law where the activation energy increases with decreasing pore size. The observed pore size dependence for the diffusion of poly(propylene glycol) in silanized nanoporous glasses can be discussed assuming interaction and confining size effects.

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“…Diffusion displacements of various molecules can be studied using the well-known 109 pulsed magnetic field gradient NMR techniques (pulsed field gradient, or PFG, and pulsed gradient spin echo, or PGSE). By modifying the conventional echo pulse sequence and by using strong pulsed field gradient amplitudes (up to 2500 ± 5000 G cm 71 ) 138,139 one can measure the diffusion coefficients of the order of 10 710 cm 2 s 71 . The measurement error is usually 5% to 10% of the measured values and depends on many factors 140,141 including finite duration of the gradient pulses 142 ± 144 and gradient-induced eddy currents, 112, 145 ± 147 local field gradients due to the presence of interfaces between materials with different magnetic susceptibilities, 148 ± 151 convection, 147 temperature errors and radiation damping effects.…”

Section: Methods Of Diffusion Studiesmentioning

confidence: 99%